1. Field of the Invention
The present invention relates to an ink jet printing apparatus for printing an image on a print medium by ejecting ink from a print head and more particularly to an ink jet printing-apparatus capable of performing a margin-free printing (or marginless printing) that prints on a print medium without leaving blank margins at ends of the print medium.
2. Description of the Related Art
In addition to an ink that adheres to a print medium for image making, normally a waste ink is also produced in an ink jet printing apparatus that is absorbed and held in an apparatus body. This waste ink is produced when performing such recovery operations as a preliminary ejection and a print head nozzle suction and when performing a printing operation without leaving blank margins at ends of the print medium (this type of printing is hereinafter referred to as a marginless printing).
(Preliminary Ejection)
In nozzles that have not performed ink ejection for many hours, ink evaporation from nozzle ends causes property changes in the ink, which in turn may result in ejection failures. To avoid this, an ink ejection not directly associated with the image making is performed at a preliminary ejection ink receiver provided outside the printing area. The preliminary ejection ink receiver typically consists of a sponge that absorbs ink and is connected with a waste ink absorber provided in the apparatus body. The preliminary ejection may also be done-to flush out mixed color inks from the nozzles.
(Print Head Nozzle Suction)
If the print head is left unused for a long period of time, bubbles may accumulate in a head liquid chamber. When a large bubble is produced, the bubble may cover the nozzle portion, rendering it unable to eject properly. Hence, in the ink jet printer, it is necessary to measure the time that has elapsed from the last head nozzle suction operation and perform nozzle suction operations at predetermined time intervals. This suction operation involves hermetically closing the head nozzle portion with a cap that communicates with a pump and operating the pump to reduce a pressure and thereby draw out ink from the head nozzles. At this time, increasing a magnitude of pressure reduction to draw out ink with a strong suction force can also discharge bubbles from the liquid chamber at the same time. The ink thus drawn out is pumped to a waste ink absorber in the apparatus body where it is absorbed and retained.
(Marginless Printing)
When performing a marginless printing (with no blank margins left at ends of the print medium), print data is used that is to be printed over an area larger than the medium and an ink ejection operation is done over and slightly beyond the print medium. Therefore, a part of the ejected ink does not land on the print medium but on a platen outside the print medium. Thus, an ink absorber (platen ink absorber) that collects the ink ejected outside the print medium is often provided In a predetermined range of the platen where excess ink may land, in order to prevent the platen from being contaminated by the excess ink.
An execution of the marginless printing as described above also produces a waste ink. Thus, the waste ink is produced not only during the recovery operation such as preliminary ejection and nozzle suction but also during the marginless printing. Therefore, in a conventional configuration that manages only the amount of waste ink generated by the recovery operation despite the fact that the waste ink is also generated during the marginless printing, the inventors have found the following problems. That is, since the configuration that manages only the amount of waste ink produced by the recovery operation cannot know the amount of waste ink from the marginless printing, it cannot check an ink overflow from the ink absorber caused by the waste ink produced by the marginless printing, thus increasing the probability of stain inside of the apparatus
To describe in more concrete terms, in a first configuration in which an ink absorber (waste ink absorber) for collecting a waste ink produced by the recovery operation and an ink absorber (platen ink absorber) for collecting a waste ink generated by the marginless printing are not communicated with each other, because all of the waste ink from the marginless printing is retained in the platen ink absorber, it is necessary to manage the amount of waste ink produced by the marginless printing so that the total amount of ink delivered to the platen ink absorber does not exceed the absorption limit of the platen ink absorber. Without this management, the ink overflow from the platen ink absorber cannot be prevented, which will increase the probability of platen stain.
On the other hand, in a second configuration in which the ink absorber (waste ink absorber) for collecting the waste ink produced by the recovery operation and the ink absorber (platen ink absorber) for collecting the waste ink generated by the marginless printing are communicated with each other, the waste ink from the marginless printing is collected through the platen ink absorber to the waste ink absorber where it is held. That is, the waste ink from the marginless printing is held in the waste ink absorber along with the waste ink from the recovery operation. Thus, in this second configuration, the total amount of waste ink in the waste ink absorber must be managed by taking into consideration the amount of waste ink from the marginless printing as well as the amount of waste ink from the recovery operation so that the total amount of ink held in the waste ink absorber does not exceed its absorption limit. As described above, unless the amount of waste ink from the marginless printing is managed along with the amount of waste ink from the recovery operation, the ink overflow from the waste ink absorber cannot be prevented, which in turn leads to an increased probability of stain inside the apparatus.
As can be seen from the above, in an ink jet printing apparatus capable of marginless printing, it is desired that the amount of waste ink produced during the marginless printing be managed for preventing the ink overflow from the ink absorber and for reducing a probability of stain inside the apparatus. Further, it is also desired that the management of the amount of waste ink produced by the marginless printing be realized in as simple a construction as possible without requiring a complicated control process.